You can't run unsigned ARM binaries on M1 Macs. Hell, you can't run un-Notarized apps on any Mac running a recent macOS release without knowing some arcane trick to open them.
They need to be ad-hoc codesigned; ie, codesigned with a certificate you made up on the fly, unapproved by any one. This is an implementation detail and nothing more; Apple likely did it to simplify how binaries are loaded.
Running un-Notarized apps is extremely trivial if you know how to use the Terminal. IMO, anything you can easily turn off if you want to is "not locked down".
You can't run unsigned ARM binaries on M1 Macs. Hell, you can't run un-Notarized apps on any Mac running a recent macOS release without knowing some arcane trick to open them.